In residential construction, flooring for wet areas (bathrooms, kitchens, laundry rooms, etc.) typically involves first creating a “sub-floor”, which is attached directly to the underlying support frame (studs and/or joists). The sub-floor typically consists of wood-based products such as particle board, press board, plywood, oriented strand board (OSB), or other such timber-based products.
In areas where tile is desired, it is common practice to attach underlayment (also known as backerboard) to the sub-floor and then affix tile on top of the underlayment. Having to haul, size, and install two materials prior to installing tile is time-consuming and increases labor costs. Also, given that the wood sub-floor is highly susceptible to water damage and lacks dimensional stability, fiber-reinforced cement (FRC) products such as water-resistant building sheets have been used as underlayments and are known in the art. Fiber-reinforced cement underlayments provide a moisture resistant barrier between the sub-floor and tile. However, if this waterproofing barrier is not installed correctly, water may penetrate through to the underlying sub-floor. The dimensional instability of the wood sub-floor could then disrupt the adhesion of the tiles to the underlayment or worse, the integrity of the underlying structure.